Trench type PIN photodetectors are formed by etching two sets of trenches simultaneously in a semiconductor substrate, the wide trenches having a width more than twice as great as the narrow trenches by a process margin; conformally filling both types of trenches with a sacrificial material doped with a first dopant and having a first thickness slightly greater than one half the width of the narrow trenches, so that the wide trenches have a remaining central aperture; stripping the sacrificial material from the wide trenches in an etch that removes a first thickness, thereby emptying the wide trenches; a) filling the wide trenches with a second sacrificial material of opposite polarity; or b) doping the wide trenches from the ambient such as by gas phase doping, plasma doping, ion implantation, liquid phase doping, infusion doping and plasma immersion ion implantation; diffusing the dopants into the substrate, forming p and n regions of the PIN diode; removing the first and the second sacrificial materials, and filling both the wide and the narrow sets of trenches with the same conductive material in contact with the diffused p and n regions.